Promise.all vs Promise.race vs Promise.allSettled vs Promise.any

JavaScript has different Promise methods for handling multiple promises. Here's what each one does.

Promise.all

Waits for all promises to resolve. If any promise rejects it fails immediately.

Promise.all([
  fetch('/api/user'),
  fetch('/api/posts'),
  fetch('/api/comments')
])
  .then(results => console.log('All done', results))
  .catch(error => console.log('One failed', error));

Use this when you need all results and cant proceed if anything fails.

Promise.race

Returns as soon as the first promise settles. Doesnt matter if it resolves or rejects.

const timeout = new Promise((resolve, reject) =>
  setTimeout(() => reject('Timeout'), 5000)
);

Promise.race([fetch('/api/data'), timeout])
  .then(data => console.log(data))
  .catch(error => console.log('Timed out or failed'));

Good for implementing timeouts.

Promise.allSettled

Waits for all promises to finish and returns everything. Doesnt reject early like Promise.all.

Promise.allSettled([
  fetch('/api/user'),
  fetch('/api/invalid'),
  fetch('/api/posts')
])
  .then(results => {
    results.forEach(result => {
      if (result.status === 'fulfilled') {
        console.log('Success:', result.value);
      } else {
        console.log('Failed:', result.reason);
      }
    });
  });

Useful when you want to try multiple things and handle successes and failures separately. This one was added in ES2020 so its relatively new.

Promise.any

Returns the first promise that resolves successfully. Ignores rejections unless everything fails.

Promise.any([
  fetch('/api/server1/data'),
  fetch('/api/server2/data'),
  fetch('/api/server3/data')
])
  .then(data => console.log('Got data', data))
  .catch(error => console.log('All failed', error));

Good for trying multiple sources and using whichever works first. Added in ES2021.

When to use what

Promise.all is the most common one. Use it when you need multiple async operations to complete before continuing.

Promise.race is useful for timeouts or when you only care about the fastest result.

Promise.allSettled is good when you want to attempt multiple operations and handle each result individually regardless of success or failure.

Promise.any is less common but useful for redundancy scenarios like multiple API servers.